Ideally, monitoring and controlling one or more of a plurality of nanosatellites relative to a reference body or reference position would allow (i) control of relative motion of each of the nanosatellites, (ii) power or energy transfer between two or more of the nanosatellites, and (iii) data communication between two or more of the nanosatellites. However, this monitoring of position requires reasonably accurate specification of vector coordinates of the nanosatellites that interact with each other. At first impression, the number of independent equations appears to be less than the number of independent variables, such as location coordinates, which presents a problem for a complete specification. This problem can be resolved in some configurations and may be extendable to other geometric configurations as well.
Electromagnetic controller satellite formation has been studied for large satellites and has been studied and constructed for small satellites. The operating distances for previous applications requires significant electrical power. For example, an implementation of single access control for a large satellite requires more than 300 Watts. A typical nanosatellite operates on 2.5-10 Watts of power, which makes a large satellite impractical for nanosatellite use.
Design of three-axis control in the prior art uses a configuration that generates a single magnetic dipole that can be oriented in any direction. When two satellites in such a system are pushing or pulling in unison, the dipoles are aligned, which does not allow relative orientation of the two satellites without use of some reaction device, such as mechanical reaction wheels.
For efficient control, at least one of a plurality of satellites requires information on relative location and relative orientation of each of the other satellites. Satellite systems in the prior art resolve this requirement by assuming that each satellite knows its own location and orientation and frequently transmits this information to a reference satellite. This is a costly process for accurate detection in a nanosatellite system. GPS or a similar process can only be used once or twice per day, because of the large associated power consumption. Each participating satellite in such a system must use a radio device to transfer this information to the reference satellite. Because of the fast response of a control system, the increasing “staleness” of the information, and the time required to transfer this information, operation may tend to destabilize the control system. For example, a satellite system recently tested on the I.S.S. required that the control system processing rate be reduced by a factor of about ten, in order to deal with this latency and avoid destabilization. The smallest electromagnet presently available measures 77 cm by 13 cm, but the smallest nanosatellite has dimensions of about 10×10 by 10 cm.
What is needed is a nanosatellite control system that avoids or minimizes the impact of these limitations: (1) large power consumption; (2) use of additional reaction wheel to manage single dipole limitation; (3) each satellite has knowledge of its location and orientation information; and (4) sensing device for each satellite determining its own location and orientation.